This invention relates to a sliding arm lock assembly particularly adapted for use in a cardiac compressor having a base platform assembly, support pillar or post and a compressor arm slidably supported by the post.
FIG. 1 of the drawings illustrates in perspective such a unit and the lock assembly 10 is adapted to be manually controlled to permit positioning the arm 12 at different positions relative post 14 and platform assembly 16. One prior art embodiment is illustrated and described in commonly assigned U.S. Pat. No. 3,364,924 issued Jan. 23, 1968. In the type of prior art embodiment described in the above identified patent, the compression arm includes a peripheral collar which is rotatable on the support post and vertically slidable when the locking means is loosened. The locking means includes either a pair of generally cylindrical abutting elements or a single cylindrical element with a threaded stud extending therefrom having a handle or the like attached to one end for manual loosening and tightening. The cylindrical element or elements include a saddle-shaped seat portion for abutment with the periphery of the post to bind the assembly when the knob or handle is tightened. To bind the assembly, the knob is rotated so that the collar presses the cylindrical element toward the post to secure and bind the assembly. While this type of lock assembly works adequately, there are several disadvantages that are significantly overcome by the subject invention. To begin with, the prior art tightening mechanisms were subject to overtightening which resulted in reduced effectiveness or failure in the threaded shaft requiring replacement of the lock assembly. Too much torque could be applied resulting in repeated over stressing of the assembly. The assembly of course has to be manipulated by a variety of different types of persons and hence too little torque advantage could easily result in certain people not being able to tighten the assembly up adequately enough under certain uses. A second distinct drawback was the propensity when adjusting the compressor arm relative the post to unintentionally lift the compressor arm up sufficiently high enough toward the upper end of the post such that the locking assembly became displaced or misaligned relative the post therefore preventing further operation until the parts were carefully aligned once more. Thus, there is a need in this art for an improved sliding arm lock assembly.